If a space is open public (as this library is), why should people be allowed to view pornography in a library, but not hold a religious meeting? Does the library not have a copy of the Bible, Koran, or Torah?

My interpretation of the doctrine of separation of Church and State is that the state must not endorse or favor one religion over another.  The doctrine should not persecute Christians who want to pray in school or the library.  It should be an argument to allow it.  By telling people what religious activities they can do and where, you are (to coin a programming term) coupling church and state.  The church is now dependent on what the state says is allowable.